The Impacts of Alternative Projection Methods on Sustainable Catch Limits Estimated from Stock Assessment Models

Data used in stock assessment models are often a year or more out of date by the time the assessment is completed, and there may be a lag in the implementation of the assessment-estimated catch limits.  Projections are often used to estimate catches during this time lag period, and also for the interval between assessments.  Projected catches are very sensitive to the terminal estimate of recruitment from the assessment, which is often highly uncertain.  Using a simulation model we explored different ways to account for uncertainty in future catch limits (either by constraining the terminal estimate of recruitment in the model, or by averaging the catch limit between current and past assessments), and how these methods interacted with the life history and recruitment variability of the target species.  Methods to dampen the effect of uncertainty in terminal recruitment estimates on the projected catch limits can help mitigate the impacts of erroneously high or low recruitment estimates, which can reduce variability in both population size and fishery landings.  This dampening effect is particularly important for species with high recruitment variability and early age of recruitment to the fishery.